The invention relates to a cementlessly implantable prosthesis with a shaft the surface of which is provided with a large number of fine pocket holes. Prostheses of this type are used for replacing bones, dental roots, joints or rigid or flexible intervertebral discs.
Cementless implants avoid negative side effects arising from reactions of the organism with polymerizing cement components, which result in a destruction of the tissue and thus in a loosening of the implant.
As described in "Neuere Werkstoffe in der medizinischen Technik", Chemie-Ingenieur-Technik 47, No. 8 (1975), pp. 327-333 or in DE-A-2,721,686, known cementlessly implantable prosthesis are often provided with a porous surface which joins tightly with the bony tissue. According to DE-A-2,154,272, a porous structure may be obtained by sinter-fusing granules or beads onto the prosthesis shaft or by cutting small pocket holes into it by means of an electron or laser beam.
EP-A-0,321,389 describes the coating of a prosthesis with a biologically active ceramics material which may be resorbed, or with a resin which remains stable when exposed to the environment of living tissue. When the ceramics material is resorbed, a porous resin structure remains into which bony tissue may grow.
Anchoring a prosthesis is known to take some time until the bony tissue has grown into the porous surface. During this time, high loads must not be exerted on the prosthesis, and there is a danger of the prosthesis to come loose again.